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An optical board reports the IN_PWR_ABN alarm though the received optical power of the pluggable optical module is below the overload threshold and within the normal sensitivity range

Publication Date:  2012-07-25 Views:  44 Downloads:  0
Issue Description
 A customer replaces the SFP optical module on a line board. The received optical power of the new optical module is �7.8 dBm. The new optical module accepts the optical power ranging from �28 dBm to 0 dBm. Therefore, the received optical power is within the normal sensitivity range. The board, however, reports the IN_PWR_ABN alarm. 
Alarm Information
 IN_PWR_ABN 
Handling Process
 1. Explain to the customer how the optical power threshold of the SFP module is read and written.
2. When the customer applies a third-party optical module, the board software cannot read the optical power threshold and has to use the default optical power threshold.
3. The default overload point for an optical module with an 80-km transmission distance is �9 dBm. Therefore, the received optical power (�7.8 dBm) is above the default overload threshold (�9 dBm) even if it is within the optical power range (�28 dBm to 0 dBm) accepted by the new optical module. As a result, the board reports the IN_PWR_ABN alarm. 
 
Root Cause
 On an optical interface board with a pluggable optical module, the software reads the optical power threshold from the specified area of the pluggable optical module. If a third-party optical module is applied, the board software may not read the optical power threshold and has to use the default optical power threshold.
Replacing the SFP optical module can change the optical power threshold provided that the new optical module is from Huawei. 
 
Suggestions
 Learn how Huawei boards work with pluggable optical modules. 

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